Metal silicides are well known for use in semiconductor processing. For example, in integrated circuit devices, metal silicides are known to be employed to reduce resistivity of contacts on the source, drain and gate regions of MOS type transistors.
A number of methods for forming silicides have been developed. U.S. Patent Application No. 2006/0014387 teaches one such method in which a silicide is formed in exposed silicon on a semiconductor wafer by a method that includes forming a thin interface layer over the semiconductor wafer. The interface layer can include Ni, Co, Ta, Ti, W, Mo, Pd, Pt or an alloy of these metals. A first low temperature anneal is performed to create the silicide. An unreacted portion of the interface layer is removed, followed by a second low temperature anneal to complete the formation of a low resistance silicide.
A problem that can occur when processing to form metal silicides is that the metals can diffuse along dislocations in the silicon lattice structure and undesirably affect the electrical performance of the circuit. Dislocations can include spike defects and pipe defects. The metal used to form the silicide, such as Ni, can diffuse along and/or gather at the defects. This metal diffusion in relation to the defects can cause, for example, increased leakage current.
Improvements in processing techniques for forming silicides are desired. For example, it would be beneficial in the art to develop new processes for reducing or eliminating the effects of metal defects in silicon devices.